This application is directed to an improved pouch packaging machine which has independently movable side and cross seals. Because the side and cross seals are independent from one another, bags of a variety of sizes can be produced on the machine and different stroke lengths and/or pressures can be used independently for the side seals and the cross seal.
In the pouch packaging industry the word "seal" has been utilized to refer to both hardware items and to actual seams formed on pouches. For the purposes of this specification the word seal, unless otherwise modified, will be made in reference to machine hardware.
Certain pouch packaging machines are known. They generally share certain common characteristics. Typically a pouch packaging machine will convey continuous rolls of front and back sealable films first through side seals to form side seams and then through a cross seal to form top and bottom seams on pouches which are being formed on the packaging machine. For an individual pouch the front and back sealable films are fed through the machine and side seams are formed by side seals. Next a bottom seam is formed by the cross seal and the pouch filled with its appropriate contents. The pouch is then completed by the formation of a top seam, also formed by the cross seal. The pouch is then severed from the moving streams of the front and back heat sealable film and is discharged from the machine.
Normally a number of pouches are made concurrently in parallel columns across the width of the machine. Thus, a plurality of side seals would be utilized to form a plurality of side seams between the front and back films as they move through the packaging machine. A cross seam is formed across the totality of the width of the plurality of parallel moving pouches. This cross seam forms the top seam on a lower pouch in each column and concurrently forms the bottom seam on the next adjacent pouch in each column. The seam formed by the cross seal is severed to separate the filled, completely formed pouch from the next adjacent empty pouch which is now in position for filling.
Each of the side seams is formed by a side seal which consists of a front and back side seal bar. The front and back side seal bars are brought together to compress and hat seal the front and back sealable film together to form the side seam. The individual side seal bars, both front and back, are of a sufficient length to form a continuous side seam along the totality of the length of a particular pouch being formed on the pouch packaging machine. To do this the front and back side seal bars must be brought together in a perfectly aligned parallel arrangement such that they exert an even pressure along the totality of their length.
Likewise the cross seal is formed by front and back cross seal bars which are brought together to squeeze the front and back heat sealable films together to form a continuous cross seal across the totality of the width of the moving columns of pouches being formed on the pouch packaging machine. As with the side seals, the pressure across the totality of the width of the cross seals must be even such that a perfect seal is formed across the totality of the front and back films.
In known pouch packaging machines the side seals and the cross seals are driven by a single prime mover such that they move in unison. As the front and back side seal bars are brought together to form side seams the front and back cross seal bars are brought together to form the top and bottom seams. In operating the pouch packaging machine, the front and back films are advanced and then they are concurrently contacted by both the side seals and the cross seal. Next the individual pouches are filled. The cycle starts over again and once again the film is advanced and the side seals and cross seals again contact the front and back films to squeeze these films together to form the seals between them.
For small pouches utilized for condiments, salad dressing and other similar food stuff the above described operation is very effective and efficient and upwards of a hundred cycles can be performed each minute. Thus on a machine, as for instance, a machine utilizing 18 inch wide film forming one and one half inch wide packaging, 12 side by side columns of individual pouches can be formed concurrently. This machine is thus capable of forming, filling and sealing well over 1,000 pouches per minute.
Since it is necessary to bring the front and back side seal bars together evenly along the totality of their length to form a perfect side seam, the length of the side seal bars has heretofore been limited. Further, since the cross seal has moved in conjunction with the side seals, the size of the packages or pouches which can be formed on a typical pouch packaging machine has also been limited. Formation of larger size pouches has been inhibited by the length of the package. It has only been possible to increase the size of the pouches by increasing the width of the pouch in order to gain additional volume in the pouch. This too has its limitations.
Since continuous rolls of film are only available in certain widths with the maximum width presently available being about 24 inches, maximum pouch size has been limited to about 64 ounces. However, additional problems are encountered when very wide pouches are made because of the spreading of the front and back film surfaces away from one another during and just after the filling operation.
The final size of any pouch formed on a pouch packaging machine is determined by the amount of contents to be held in the pouch and how the contents will be disbursed from the pouch. Thus, the geometry of the pouch is sometimes highly dependent upon what the pouch will ultimately contain. Normally since pouches are somewhat elongated to facilitate dispensing of the contents thereof, the side seams will be of a greater overall dimension than the top and bottom seams resulting in the overall square surface area of the totality of the front and back side seal bars over which sealing pressure is applied being greater than that of the front and back cross seal bars.
In prior known pouching machines which are all driven by a single prime mover, since the overall area of the side seal bars is greater than the overall area of the cross seal bars, or vice versa, the pressure exerted on the side seal bars against the heat sealable films will be less (or more) than that exerted by the cross seal bars. This leads to different seal characteristics of the front and back heat sealable films along the side seams as opposed to the top and bottom seams. Since the specifications of the weakest seam must be considered, heretofore certain trade offs would have to be made to insure that the weakest seam was of sufficient strength yet the pressure exerted on the other seam or seams, whether it be the cross seam or the side seams, was not overly excessive as to detract from the characteristics of the heat sealable films and the seams formed therein.
Furthermore, since the side seals and the cross seals moved in unison and were driven by a single prime mover, unless very sophisticated mechanical linkages were resorted to, in moving toward and away from one another the front and back side seal bars had to move the same distance as the front and back cross seal bars. While in small flat pouches this does not present too great a problem, in larger pouches which tend to have bulging contents, it is necessary to move the cross seal bar a sufficient distance to allow the filled pouch to descend through the cross seal bar prior to forming the top seam on the filled pouch. The side seal bars however are located upstream from the filling station and there is no reason for them to have to move the same distance as the cross seal bars since they only have to account for the thickness of the unfilled pouches, i.e. the thickness of the flat front and back films. Thus, heretofore to accommodate the movement of the cross seals, there has been excessive movement of the side seals through distances much greater than is needed for the passage of the unfilled pouches between the side seals.